This invention pertains to an improved method and apparatus for monitoring, recording, and analyzing the performance of electric motor-operated pumps and valves and pneumatically operated valves. It more particularly relates to the identification and monitoring of a valve's movement and related characteristics during a start-up or single stroke opening and closing cycle, and of its characteristics during a single stroke shutting off and opening up cycle.
A prior art approach to measuring and monitoring various characteristics of a machine or valve is to use a variety of transducers and micro switch position monitors with analog and discrete output signals associated therewith. Often in the power industry the performance of a valve is principally established by its time to open or close. Decisions relating to the repair and replacement of a valve are most commonly made by independent evaluation of its stroke time and evaluation of seat or stuffing box leakage.
These prior art approaches suffer the disadvantages of requiring many modifications and attachments to a pump or valve. These modifications and attachments are cumbersome, expensive and sometimes intrusive upon the mechanical performance. If left in place, the monitoring devices are subject to damage and drift. The resulting data obtained during the test program on the movement of the pump or valve do not in some instance represent the service conditions of the valve. For example, in valves inside the containment of a nuclear power plant, the condition of a particular valve and pump with repsect to flow through the device, temperature of the device or the driver for the valve, and pressure are often not simulated during a testing cycle but rather are tested by normal plant operation or during accident situations. The internal atmosphere and conditions inside the nuclear containment often present a physical barrier and restrict access to individual line and prohibit the placement of measurement devices. Even in the case where a measurement of a pump or valve parameter is possible in the prior art, such individual ad hoc events are precluded or were restricted when compared to the optimum action of analyzing or comparing the trend of the pump or valve's performance under varying plant conditions. The limitations imposed on currently available instrument penetrations in Light Water Nuclear Reactor plants also present a physical, and sometimes a signal impenetrable, barrier to measuring many parameters of a valve's performance during operation.
In addition to attempting to monitor the conditions of a valve or pump during a prescribed operational process, there is also a need to protect the device against damage due to overload, improper adjustment and the like. The prior art methods with respect to motors and apparatus, which rely on measurements of the electrical current or average power consumption of the valve driver or pump motor, may be subject to greater variations than those caused by an abnormality. In other cases, the peak power consumed by the motor/driver may not change significantly in the presence of a deviation from a normal operation parameter of the pump or valve when the current and average power consumption show such a deviation. In addition, current actuated devices used in the prior art are insensitive to power changes at constant voltage which are manifested as changes in power factor.
U.S. Pat. No. 4,690,003 to McNennamy et al. discloses a motor operated valve analysis and testing system. This system requires a mechanically intrusive device placed inside the valve. The method also includes a multiple stroke analysis in order to determine the operating characteristic of the valve. The current supplied to the valve driver is monitored. However, the torque of the valve is measured by the mechanically intrusive device. U.S. Pat. No. 4,646,556 to Courcoux et al. discloses a process and apparatus for testing a pilot operated safety valve. A mechanically intrusive device is used in conjunction with the hydraulically actuated valve to measure the pressure in the hydraulic supply line to the valve. Also, force generated by the valve is measured by another device. The force and pressure are plotted against time. U.S. Pat. No. 3,779,457 to Cornyn, Jr. et al. discloses a data normalizing method for hydraulic steering pumps. The system measures the speed of the motor driving a pump, the hydraulic fluid temperature at the pump outlet, the pressure of the fluid, the flow rate and the back pressure. This information is synchronized with respect to time and displayed. U.S. Pat. No. 4,002,065 to Lardi et al. discloses a steam turbine valve positioning system that monitors flow through a valve versus valve lift. U.S. Pat. No. 4,694,693 to Gerlowski discloses a system for testing check valves using pressure sensors in the lines. U.S. Pat. No. 2,477,395 to Sunstein discloses an apparatus for continuously predicting a trend in observed data by utilizing a mechanical vice computing the root means square of variation of data applied to the device. U.S. Pat. No. 4,455,012 to Gupta discloses a remotely controlled valve that is controlled by a microprocessor. The current of the motor drive for the valve is sensed and a timing circuit ignores starting surges. U.S. Pat. No. 4,364,111 to Jocz discloses an electronically controlled valve actuator that senses the torque feedback from a valve driver. An optical sensor on the valve generates an input signal to a microprocessor indicative of the position of the valve. The torque is measured by strain gauges attached to the motor output shaft. U.S. Pat. No. 3,839,628 to Higgins et al. discloses a method and apparatus for analyzing and monitoring the performance of machines and processes driven by electrical motors. The current supplied to the electrical motor is monitored as well as the voltage across the power supply lines running to the motor. A power factor is obtained based upon the voltage current. U.S. Pat. No. 1,449,458 to Sutermeister discloses an apparatus for manufacture of ice cream which detects the current applied to the motor turning the paddles in an ice cream maker. U.S. Pat. No. 4,155,116 to Tawfik et al. discloses a digital control system including built in test equipment. The system is responsive to analog and discrete input signals and for generating test signals. U.S. Pat. No. 4,057,714 to Fork et al. discloses a durability or service-life monitoring device for a turbogenerator shaft. The current generated by a turbine driven generator and the voltage across the generator output lines are applied to a circuit which develops a power factor. A device sensing the angle of the turbine blades provides an indication of the torque generated by the turbine and applied to the generator. The torque and the power factor are used in a control circuit. U.S. Pat. No. 3,130,581 to Schulman discloses a torque and speed measuring instrument. Torque is calculated based upon the alternating current applied to a torque generator. U.S. Pat. No. 4,682,491 to Pickard discloses an apparatus and method for testing prosthetic heart valves. This device measures flow and pressure from the implantable pump in the heart valve. U.S. Pat. No. 4,202,209 to Holmes discloses a shock suppresser valve test system and method. The velocity of the fluid flowing to the shock suppresser is used in the system. The velocity is an indication of the required flow rate within the shock suppresser necessary to close the shut-off valves.